I can't see any way to sync Tasks I set up in S-Planner with any other devices or cross platforms. I know that Google Tasks don't sync (shaking head in dismay at that one).
Due to the recent problems with no Sync feature in Kies3, I've had to temporarily resort to using other Apps to sync my S Planner calendar with Microsoft Outlook.
Today Samsung have returned Sync to Kies3, which is great, however...
During my use of one particularly rubbish app (that shall remain unnamed), I now have duplicate entries in S Planner for every single event.
Just a fun topic, maybe will encourage discussion of to-do list apps in a different way.
For my main to-do list, I use Google Tasks on PC which syncs with Tasks by Team Tasks (pro version) on Android. Traditional syncd to-do. Has most of what I want in a simple solid, syncable, indentable/nestable categorized note list with alarms.